1. Field of Invention
This invention relates to surface coating compositions and, in particular, to asbestos-free, dry wall coating compositions.
2. Brief Description of the Prior Art
Surface coating compositions for the common dry wall construction generally require a fibrous filler for working characteristics such as nonleveling and lubricating properties. Heretofore, chopped asbestos fibers have been universally used because of the abundance and superiority of asbestos over other fibers such as fiber glass and wood pulp. Increasing concern of environmental and occupational health hazards has focused attention on the hazardous nature of asbestos since this material has been isolated and identified as the causative factor in various diseases including lung cancer. Significant concentrations of air-borne asbestos fibers occur when the compositions, which are commonly shipped and stored as a dry powder, are blended with water to prepare the coating composition, and when surfaces treated with the compositions are sanded for final finishing of building interiors. The Occupational Safety and Health Administration has prescribed very limited permissible concentrations of air-borne asbestos fibers and these concentrations will, shortly, preclude the use of asbestos fibers in the various dry wall surfacing compositions.
Attempts have been made to eliminate asbestos fibers from surface coating compositions by increasing or modifying the contents of the various other fillers often employed in the coating compositions as typified by U.S. Pat. No. 3,391,453. Despite these attempts, there is generally a need for a fibrous filler substitute for asbestos fibers that will provide surface coating composition having working characteristics and properties that are generally the same as the asbestos-containing compositions, thereby avoiding the retraining or reeducation of the workmen who apply these compositions.